Polyesters such as poly(ethylene terephthalate) (PET) have excellent thermal and mechanical properties. The main applications of PET include the manufacture of video and audio tapes, textiles, X-ray films, and food packaging, particularly for water and soft-drink bottles. In 2009, the world consumption of PET packaging alone was about 15.5 metric tons, and it has been estimated to increase to almost 19 metric tons by 2017, a 5.2% growth rate per year. Despite its many benefits, items made from PET have typically been used for a short period of time and then disposed of, especially water and soft-drink bottles.
Accumulation of the resulting waste from petroleum-based plastics such as PET has become an environmental concern worldwide. PET has been present in nature for only a comparatively short period of time, and microorganisms have not yet developed new enzyme structures to consume them. As a result, articles made from PET often end their life cycles either buried in landfill sites or burned, which can generate unwanted gaseous emissions. Therefore, other end of life solutions for PET, such as recycling, have been proposed.
One approach to recycling is based on the depolymerization of PET. Many processes for PET depolymerization have been studied, depending on the end use of the reclaimed products. Each process has its own advantages and disadvantages. A disadvantage of some methods is difficulty in separating the reclaimed products in a sufficiently pure state for further use. There accordingly remains a need in the art for improved methods for the recycling of PET based on depolymerization, particularly purifying depolymerization products.